WO2005021359A1

WO2005021359A1 - Controller for electric power steering device

Info

Publication number: WO2005021359A1
Application number: PCT/JP2004/012695
Authority: WO
Inventors: Kazuhiro Kumaido; Yuusuke Itakura; Yuho Aoki; Nobuhiro Kubo
Original assignee: Nsk Ltd.; Nsk Steering Systems Co., Ltd.
Priority date: 2003-08-28
Filing date: 2004-08-26
Publication date: 2005-03-10
Also published as: US20070000717A1; EP1666339B1; EP1666339A1; US7559405B2; EP1666339A4

Abstract

A controller for an electric power steering device, capable of achieving safe steering operation even when an output value of a torque sensor that detects steering torque of a steering wheel is abnormal. The safe steering operation is achieved without giving clumsy feeling to steering operation with a failure determination fixing time period that is long enough to prevent miss-detection of a torque sensor failure secured.

Description

Description Control device for electric power steering system Technical field

The present invention relates to a control device for an electric power steering device, and particularly to an electric power steering device that can continue control using an alternative torque value when a torque sensor becomes abnormal, and that can reliably detect a failure of the torque sensor. Related to a control device. Background art

An electric power steering device that applies a steering assist force to a vehicle steering device by a motor rotating force is a device that transmits a driving force of a motor to a steering shaft or a rack shaft by a transmission mechanism such as a gear or a belt through a speed reducer. It is designed to provide help.

An example of the configuration of such an electric power steering device is shown in FIG. 1 and will be described. The steering shaft 101 of the steering handle 101 is connected to the deceleration gear 103, the universal joint 104a and 104b, and the tie rod 106 of the steered wheels via the pinion rack mechanism 105. Are linked. The shaft 102 is provided with a torque sensor 107 for detecting the steering torque of the steering wheel 101, and the motor 108 for assisting the steering force of the steering wheel 101 is provided with a deceleration gear. It is connected to shaft 102 via 103. The motor control of the electric power steering device is performed by inputting a torque value detected by the torque sensor 107, a vehicle speed detected by a vehicle speed sensor (not shown), or a rotation angle of the motor detected by the Hall sensor 110 or the like. Is controlled by the control unit 109. Control Unit 109 mainly It is composed of a CPU, and motor control is executed by a program inside the CPu.

An example of a control system for controlling the motor 108 of such an electric power steering device will be described with reference to FIG. In FIG. 2, a current command value calculator 120 inputs the torque value detected by the torque sensor 107 to calculate a current command value I ref, and calculates a difference between the detected motor current value Im and the detected current value Im. The subtraction unit 122 calculates the duty ratio, the current control unit 122 determines the duty ratio, and the motor drive unit 123 drives the motor 108 by executing the PWM control according to the duty ratio.

In such an electric power steering device, control of the electric power steering device is executed on the assumption that the torque value detected by the torque sensor 107 is correctly detected. However, in practice, the torque sensor 107 also fails, and when an abnormal torque detection value is input, it may cause an abnormal operation to the steering wheel operation. Measures have been taken.

For example, Japanese Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2000-3110) adopts a control method as shown in FIG. 3 and responds abnormally to the torque value output by the torque sensor. . That is, when the torque value output by the torque sensor becomes abnormal, if the abnormality continues for a predetermined time (tA), the steering assist force command value, which is the output value of the current control calculation based on the torque value, is cut off. I will. If the abnormality continues for a predetermined time (tB) for a longer time, the control system shuts off the motor drive power.

FIG. 4 shows the relationship between the torque value and the motor current when the torque sensor generates a ground fault and the torque value output from the torque sensor becomes zero in such a control method. In the case of this control method, the steering assist force command value is determined based on the output value of the abnormal torque sensor for a predetermined time (tA). , The steering assist force becomes abnormal and the steering wheel moves unintentionally. Further, if the abnormality continues for a predetermined time (tB) or more, the motor power is shut off. If a large torque is applied to the steering wheel, the torque suddenly changes, which is not preferable.

As another countermeasure, there is a control method disclosed in Japanese Patent Document 2 (Japanese Patent Application Laid-Open No. 2000-3292628). Patent Document 2 discloses that when a serious abnormality such as a voltage drop or an instantaneous interruption occurs in the power supply of the torque sensor, the fail switch is opened, and the torque value before the fail switch is opened is held as the torque value output from the torque sensor. Then, the steering assist force command value is obtained by multiplying the held value by the output gain. In addition, since the subsequent steering assist force is controlled so as to gradually decrease, the steering assist force does not suddenly change. Fig. 5 shows the relationship between the output of the torque sensor (torque value) and the motor current when the torque sensor fails when such a control method is used, for example, when the ground fault occurs in the torque sensor. The maximum negative current flows through the motor from the occurrence of the failure until the failure is determined, but after the failure is confirmed, the motor current is gradually reduced from the torque immediately before the occurrence of the failure. Such a sudden change in torque does not occur.

However, if the torque value causes chattering and a ground fault occurs as shown in Fig. 6, when the output value of the torque sensor is sampled by the AD converter, a value like a black circle may be sampled. . In such a case, if the sampling value of the black circle does not fall below the threshold value for detecting a ground fault, the occurrence of a ground fault cannot be detected, and the control is continued as it is. After the ground fault is detected, the motor current gradually decreases from the torque value immediately before the occurrence of the fault.However, the motor current gradually decreases from the unstable torque value due to chattering. The reduction starts from the torque opposite to the torque, which is not desirable. Further, in the method of Patent Document 2, an abnormal current flows through the motor during the determination period from the occurrence of a failure to the determination of a failure, so that the determination period of the failure determination cannot be made too long. However, in order to prevent erroneous fault detection and ensure fault detection, there is a contradiction that the fault determination time should be as long as possible, which has been a problem.

When the torque value, which is the output of the torque sensor, becomes abnormal, the conventional control method causes the steering assist force to become abnormal because control is performed based on the abnormal torque value until the failure of the torque sensor is confirmed. was there.

In addition, even when an alternative torque value was used instead of an abnormal torque value, there was a problem that an appropriate alternative torque value was not calculated. As a result, if the output of the torque sensor becomes abnormal, the steering wheel performs an unintended movement of the driver, giving a driver an uncomfortable feeling of operating the steering wheel. Further, during the determination period from the occurrence of a failure to the determination of a failure, an abnormal current flows through the motor, so that the determination time of the failure determination cannot be prolonged. There was a problem that caused false detection. In particular, in the chattering phenomenon that occurs when the wiring for transmitting the torque value detected by the torque sensor is likely to be broken, there has been a problem that it is difficult to correctly control the torque of the electric power steering device.

The present invention has been made in view of the circumstances described above, and a first object of the present invention is to provide a torque sensor that is long enough to prevent erroneous detection of a torque sensor failure even when the output value of the torque sensor becomes abnormal. An object of the present invention is to provide a control device for an electric power steering device that can ensure a safe steering operation while ensuring a failure determination confirmation period without giving a feeling of strangeness to the steering operation.

Further, a second object of the present invention is to provide a control device for an electric power steering device which can safely switch between an output value of a torque sensor and an alternative torque value used in the event of an abnormality, even when a plurality of torque abnormality detecting means are present. To provide And there.

A third object of the present invention is to provide a control device for an electric power steering device capable of accurately estimating an alternative torque value used for control during an abnormal period of a torque sensor. Disclosure of the invention

The present invention provides an electric power steering that includes a motor that applies a steering assist force to a steering system of a vehicle, and a torque sensor that detects a steering force acting on a handle, and controls the motor based on an output value of the torque sensor. The present invention relates to a control device for a switching device.

The object of the present invention is to provide a torque abnormality detecting means for detecting an abnormality of the torque sensor, and an alternative torque value calculating means for calculating an alternative torque value when the torque abnormality detecting means detects an abnormality. This is achieved by using a control device that controls the motor based on the alternative torque value when a torque sensor abnormality is detected.

The object of the present invention is to provide a torque abnormality detecting means for detecting an abnormality in the output value of the torque sensor, and a substitution based on a past normal output value of the torque sensor before the output value of the torque sensor becomes abnormal. A torque input processing unit comprising a torque value calculating means for calculating a torque value, wherein when the output value of the torque sensor is abnormal, the torque input processing unit is used based on the alternative torque value instead of the output value of the torque sensor. This is achieved by using a control device that controls the motor.

In addition, the above object is to provide a torque failure determination means for determining that the torque sensor is faulty if the output value of the torque sensor continues to be abnormal for a certain period of time, wherein the output value of the torque sensor is abnormal. At this time, even before the determination that the torque sensor is faulty, the torque sensor This is achieved by using a controller that controls the motor based on the alternative torque value instead of the output value.

The object of the present invention is a plurality of torque abnormality detecting means for detecting an abnormality of the torque sensor based on a ttl force value of the torque sensor; and a normal torque in the past before the output value of the torque sensor becomes abnormal. An alternative torque value calculating means for calculating an alternative torque value based on an output value of the sensor; and when the plurality of torque abnormality detecting means determine that the torque abnormality is abnormal, the alternative torque value is substituted for the output value of the torque sensor. Controlling the motor based on the torque value; controlling the motor based on the alternative torque value; determining that all of the plurality of torque abnormality detection means are normal; replacing the alternative torque value with the alternative torque value; This is achieved by using a control device that performs control using the output value of the torque sensor.

The object of the present invention is to provide a motor control system comprising: a plurality of torque abnormality detecting means for detecting abnormality of the torque sensor based on an output value of the torque sensor; This is achieved by establishing a determination that the torque sensor is faulty when the period for determining that exceeds the predetermined time T1.

The object of the present invention is to provide a plurality of torque abnormality detecting means for detecting abnormality of the torque sensor based on an output value of the torque sensor, wherein at least one of the plurality of torque abnormality detecting means is abnormal. This is achieved by determining that the torque sensor has failed when the determination period continues to exceed the predetermined time T3.

The object of the present invention is to provide a main torque detection value based on an output of the torque sensor.

Main torque detection means for detecting Tm; auxiliary torque detection means for detecting an auxiliary torque detection value Ts based on the output of the torque sensor;

Torque abnormality detecting means for detecting abnormality of Tm or the auxiliary torque detection value Ts And the previous normal main torque detection value Tm and the main torque detection value Tm or the auxiliary torque detection value Ts before the main torque detection value Tm or the sub torque detection value Ts becomes abnormal. And an alternative torque value calculating means for calculating an alternative torque value Ta based on a past normal auxiliary torque detection value Ts before the abnormality occurs, wherein the main torque detection value Tm or the auxiliary torque detection value is provided. This is achieved by using a control device that controls the motor based on the alternative torque value Ta instead of the main torque detection value Tm when Ts is detected to be abnormal. Brief Description of Drawings

FIG. 1 is a configuration diagram of a general electric power steering device.

FIG. 2 is a block diagram showing an example of a control system of a conventional electric power steering device.

FIG. 3 is a block diagram showing an example of a conventional electric power steering device that copes with a ground fault of a torque sensor.

FIG. 4 is a diagram illustrating an example of an output result of a motor current when a ground fault occurs in the torque sensor.

FIG. 5 is a diagram showing another example of the output result of the motor current when the ground fault of the torque sensor occurs.

FIG. 6 is a diagram showing an example of a motor current output result at the time of chattering failure of the torque sensor.

FIG. 7 is a control block diagram showing a first embodiment of the present invention.

FIG. 8 is a flowchart showing an operation example of the torque input processing unit of the first embodiment.

FIG. 9 is a flowchart showing an example of an operation for updating a past torque value. Fig. 10 shows that the current value estimated from the past torque value is used as the substitute torque value. 9 is a flowchart showing an operation example of substituting and substituting.

FIG. 11 is a diagram showing an example of an output result of a motor current when the torque sensor has a ground fault in the second embodiment of the present invention.

FIG. 12 is a view showing an example of a motor current output result at the time of failure in which a torque sensor has a chattering phenomenon in the second embodiment of the present invention.

FIG. 13 is a diagram showing the principle of current value estimation using the n-th order equation.

FIG. 14 is a diagram showing the principle of current value estimation using the least squares method. FIG. 15 is a control block diagram showing a second embodiment of the present invention provided with a plurality of torque abnormality detecting means.

FIG. 16 is a time chart showing an example of an output signal of each torque abnormality detecting means when the torque sensor is abnormal.

FIG. 17 is a control block diagram showing an example of an apparatus provided with a torque sensor failure detecting means using the alternative torque value control according to the present invention.

FIG. 18 is a control block diagram showing an example of an apparatus provided with a torque sensor failure detecting means without using the alternative torque value control according to the present invention.

FIG. 19 is a control block diagram showing a third embodiment of the present invention.

FIG. 20 is a flowchart showing an operation example of the torque input processing unit. FIG. 21 is a flowchart showing an example of an update operation of the past main torque detection value Tm and the past auxiliary torque detection value Ts.

FIG. 22 is a flowchart showing an operation example of calculating an alternative torque value from the past main detected torque value Tm and the past auxiliary torque detected value Ts. FIG. 23 is a diagram showing an example of an output result of a motor current when the torque sensor has a ground fault in the third embodiment of the present invention.

FIG. 24 is a diagram showing an example of an output result of a motor current when a failure occurs in which a torque sensor has a chattering phenomenon in the third embodiment of the present invention. FIG. 25 is a block diagram showing an embodiment of a torque input processing unit when a plurality of torque abnormality detecting means are provided. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 7 is a control block diagram showing a first embodiment of the present invention. The torque value detected by the torque sensor 107 is not directly input to the current command value calculation unit 120, but is input to the torque input processing unit 10 and the output value is input to the current command value calculation unit 120. Is entered. The current command value calculation unit 120 calculates the current command value I ref, calculates the difference from the motor current detection value Im by the subtraction unit 121, and determines the duty ratio by the current control unit 122. The motor drive unit 123 drives the motor 108 by executing the PWM control according to the duty ratio.

When the torque value output from the torque sensor 107 is normal, the torque input processing unit 10 operates so that the torque value is input to the current command value calculation unit 120. In this case, a substitute torque value is calculated, and the substitute torque value is input to the current command value calculation unit 120.

The torque input processing unit 10 is composed of torque abnormality detecting means 10-1; alternative torque value calculating means 10-2; torque failure determining means 10-3; and a selection switch 1 ◦-4. . The torque failure determination means 10-3 determines that a failure occurs if the output value of the torque sensor 107 becomes abnormal and the abnormality continues for a certain period of time. The limiter 11 provided at the subsequent stage of the current command value calculation unit 120 gradually reduces the motor current when the torque failure determination means 10-3 determines that a failure has occurred ( It has a function to narrow down the limiter value for the purpose of slash processing. Note that the torque failure determination means 10-3 need not necessarily be incorporated in the torque input processing unit 10. In this embodiment, since the output result of the torque abnormality detecting means 10-1 is used, the torque failure The determination means 10-3 is incorporated in the torque input processing unit 10. Also, the method of gradually reducing the motor current is not limited to the limiter 11. For example, by multiplying the current command value I ref, which is the output of the current command value calculation unit 120, by the gain G and reducing the gain G from 1 to 0, the value of G It gradually decreases from the value I ref toward zero.

The operation of the torque input processing unit 10 will be described with reference to the flowchart of FIG. The torque value T, which is the output value of the torque sensor 107, is read via an A / D converter (not shown) (step S1). Next, it is determined whether the torque value T is normal or abnormal (step S2). The normal / abnormal judgment value Treff can be considered variously. For example, if a value equal to or greater than a threshold value or a threshold value that cannot be obtained with a normal torque value is determined to be abnormal. Or, if it suddenly changes discontinuously, it is considered abnormal. Abnormal torque values include the output voltage being fixed to zero or the power supply voltage, offset abnormalities (abnormalities that are biased by (T +) and α), and torque amplifier abnormalities ((Κ · Τ ), The operational amplifier may be defective). If the torque value 異常 is not abnormal, the abnormality detection counter is cleared (step S3).

This abnormality detection counter counts when an abnormality of the torque value 検出 is detected, and does not immediately judge that a failure has occurred in the torque sensor just once a failure has been detected. As will be described later, it is determined that the torque sensor has failed only when the count number of the abnormality detection counter exceeds the set value. Next, the update routine of the past torque value is called, and as shown in FIG. 9, the values 直前 1, η2, Τ3, Τ, Τ5 of the immediately preceding η sample, for example, five samples are updated (step S4). Then, since the torque value is not abnormal, the torque value 算出 is calculated using the torque value as the torque input processing unit 10 (step S5). Since the torque value T is not abnormal, the current command value calculation unit 120 Calculate the current command value I ref based on the torque value T instead of the substitute torque value.

On the other hand, if it is determined in step S2 that the torque value T is abnormal, the abnormality detection power counter is counted up once (step S6). Next, it is determined whether or not the count value N of the abnormality detection counter is larger than a set value (Step S7). If the count value N is larger than the set value, it is determined that the torque sensor 107 has failed. If the count value N is equal to or less than the set value, it is not determined that the torque sensor 107 has failed. However, since the torque value is abnormal, the torque value T cannot be used as an output value of the torque sensor 107 in the current command value calculation unit 120. Therefore, an alternative torque value is set instead of the torque value T (step S8).

Here, the substitute torque value needs to be the current normal torque value predicted from the past torque value, and there are several methods for calculating the substitute torque value. The substitute torque value is calculated using n (natural number) samples of past normal torque values. For example, as shown in FIG. 10, an expected present value is obtained based on past five samples of normal torque values, and is used as an alternative torque value (step S11). For example, average the torque values T1, T2, Τ3, Τ4, Τ5 of the past five samples, and average value Tm = (T1 + T2 + T3 + T4 + T5) / 5 Is an alternative torque value. The method of calculating the alternative torque value will be described later in detail. Here, it has been described that the normal torque value in the past is used, but this is secured by the routine for updating the past torque value in step S4.

The substitute torque value obtained in this way is replaced as a substitute for the abnormal torque value (step S9). Then, instead of the output value of the torque sensor 107, this alternative torque value is input to the current command value calculation unit 120 (step S5). Motor 1 08 is controlled by alternative torque value As a result, it is possible to avoid an abnormality in the steering assist force that occurred when the control was performed with an abnormal torque value.

Another important point is that even before the determination that the torque sensor 107 has failed is determined, control is performed using an alternative torque value instead of using an abnormal torque value for control. It is. In the past, the motor was controlled by substituting an alternative torque value after determining the failure of the torque sensor and then determining it.Before determining the failure, control was performed based on the abnormal torque value. An abnormal steering assist force was generated, giving an uncomfortable feeling to the steering wheel operation.

If the abnormality of the torque sensor 107 continues, the torque value is determined to be abnormal (step S2), the abnormality detection counter is counted, and the count value is increased (step S6). If the abnormality of the torque sensor continues further and the count value N of the abnormality detection force counter exceeds the set value, it is determined that the torque sensor 107 has failed (step S7). When it is determined that the torque sensor has failed, control for gradually reducing the motor current is executed to prevent a sudden change in the steering assist force (step S10). As a method of gradually attenuating the motor current, a limiter 11 is provided at the output of the current command value calculator 120 while the alternative torque value is kept constant, and the limiter value of the limiter 11 is set. The motor current may be gradually attenuated by gradually reducing the motor current, or the motor current may be gradually attenuated by gradually reducing the torque value of the alternative torque value.

FIG. 11 shows the relationship between the torque value, which is the output of the torque sensor when the output value of the torque sensor 107 suddenly becomes zero, and the motor current using the torque input processing unit 10 of this embodiment. It is a figure showing the relationship. Even if the torque value suddenly becomes zero, the substitute torque value is immediately used instead of the abnormal torque value, so that the motor current maintains the value immediately before the torque value became abnormal. The motor current remains at the previous value until it is determined that the torque sensor has failed. After it is determined that the torque sensor has failed, the motor current is gradually attenuated. Compared to Fig. 4 and Fig. 5 showing the results of the conventional control method, the motor current does not reverse the polarity immediately before the torque value becomes abnormal, giving a sense of incompatibility to the handle operation Never.

Using the torque input processor 10 of the present embodiment, when the output value of the torque sensor 107 causes chattering and fails, the output torque value of the torque sensor (worst case) and the motor current are used. The relationship is shown in FIG. When it is determined that the torque value is abnormal due to chattering of the torque value, a substitute torque value is calculated using the past normal torque value, and the motor current is controlled based on the substitute torque value. Therefore, the motor current outputs a current that does not greatly differ from the motor current immediately before chattering occurs. Furthermore, after the failure determination is confirmed, the motor current is gradually attenuated. This result is compared with Fig. 6 using the conventional control method. In the case of the conventional control method, a motor current having a polarity opposite to that before the torque sensor output becomes abnormal is generated, and thereafter, the motor fluctuates, resulting in an undesirable result for the driver. It is good to gradually attenuate the motor current after the failure is confirmed, but it is not preferable because the motor current immediately before the attenuation attenuates from the current of the opposite polarity. However, in the present invention, even in the worst case, the control is clearly preferable to the steering of the steering wheel as compared with the conventional control method.

In the above embodiment, the alternative torque value is obtained by using a simple average of the past five samples. However, the alternative torque value may be calculated by other methods such as the least squares method. There are a method of calculating the current value by calculating an expression, a weighted averaging method, and the like. These will be described below.

First, a method of calculating the alternative torque value by creating the following equation (n_l) from n past samples will be described. For example, the past 3 as shown in Fig. 13 Sample _{_{(T 0, T 1; T}} 2) from creating a quadratic, to predict the current value T ₃ performs the following calculation.

[Number 11

T d = a · t ² + b · t + c When the above equation 1 is used, it is necessary to obtain the following equation 2 to calculate a, b, and c.

[Equation 2] v,. ,

t * 1 source ¹ "Bruno 2 Bruno

Therefore, the current value T ₃ is calculated as shown in Equation 3 below.

[Number 3]

T _s = a + bt 3 + C

In the actual calculation, the inverse matrix part can be calculated in advance. For example, the inverse matrix part for the past three samples is as shown in Equation 4 below.

[Number4] '

T = (l 1 3 3 »

, 2 no Next, a method of calculating an alternative torque value using the least squares method will be described. A linear equation is created by the least squares method from the recursive n samples of the past torque value, and the current value is predicted to set an alternative torque value. In the case of the above-described method of calculating the alternative torque 镡 by the n-th order expression, since the past torque value includes noise, it may not be possible to obtain an optimum present value by strictly fitting to the n-th order expression. Therefore, each coefficient is calculated by the least square method. For example, to create a linear expression from the past three samples and predict the current value, the following calculation should be performed.

Forecasting the current value means the past time t in Fig. 14. , The torque value T ₀ at t had t _2, T _1; is T ₂ that the torque value T ₃ in force et present time t ₃ Mel determined.

[Number 5]

To find the coefficients a and b with Τ = a · t + b, solve the simultaneous equations of Equation 6 below.

[Number 6]

V, '∑t; r ヽ

No, Rono

Therefore, in the case of the past three samples, the following equation 7 is obtained using the retrograde example.

[Number 7]

In an actual calculation, the inverse matrix can be calculated in advance. As a result, each coefficient is as shown in Equation 8 below.

[Equation 8]

Τ ₂

Regardless of the method of least squares or the method using the following equation, the form of the final calculation of the alternative torque value is a coefficient such as T = aT1 + bT2 + cT3 + d And the torque value in the past, so there is not much computational burden on the CPU.

Next, the weighted averaging method will be described. In the weighted averaging method, the torque values shown in FIG. 13 are weighted in order from the past. For example old order torque value T have _{_{_{Τ 2, Τ 3, Τ 4}}} , a T _5, if the weight for example a, b, c, d, and e, alternate torque value T is as the following equation 9.

[Number 9]

_{T = (a - T x +} b - T 2 + c - T 3 + d - Τ, + e · T K) is a / (a + b + c + d + e). Here, assuming that the weights a, b, c, d, and e are, for example, 84, 21 and 1, respectively, Equation 9 becomes Equation 10 below.

[Number 1 0]

T = (8 T, + 4Τ 2 + 2 T + T 4 + T R) / 1 According to 6 described above embodiment, when the torque value is the output of the torque sensor becomes abnormal, a soon abnormal Since the motor of the electric power steering device is controlled using the correctly predicted alternative torque value instead of the torque value, the electric power steering device does not have any abnormality in the steering assist force even in one cycle. One steering device can be controlled correctly. Furthermore, according to the present embodiment, since there is no abnormality in the steering assist force even in one cycle, erroneous detection can be prevented without any problem even if the time for determining that the torque sensor or the like is faulty is long.

In the conventional control method, the control is performed using an abnormal torque value until the output abnormality of the torque sensor is detected, so that the steering assist force becomes abnormal, or the setting of the substitute torque value is a value that correctly predicts the current value. However, there was a problem that the steering assist force became abnormal. In addition, since the steering assist force becomes abnormal, the determination time until the torque sensor or the like is determined to be faulty cannot be extended, and there is a problem that the torque sensor fault is erroneously detected. According to the above, these conventional problems can be solved. Next, a description will be given of a second embodiment capable of safely switching between the output value of the torque sensor and the alternative torque value used in the event of an abnormality even when there are a plurality of torque abnormality detecting means.

The control of the alternative torque value when there are a plurality of torque abnormality detecting means will be described with reference to FIG. The difference between the control block diagram in Fig. 7 and the control block diagram in Fig. 15 is that the configuration of the torque input processing unit 10 and the torque sensor are the same as the torque sensor 107, except that a torque sensor 107A is added. It is a point that has been. That is, in the present embodiment, the torque sensor is configured as a dual system of the main torque sensor 107 and the auxiliary torque sensor 107A.

First, an example in which a plurality of, for example, three types of torque abnormality detection means 10-1A, 10-1B, and 10-1C are provided as torque abnormality detection means will be described. The torque abnormality detecting means 10-1A detects whether the value of the main torque sensor 107 is normal or abnormal. The principle of the detection is that if the main torque sensor 107 is normal, the output torque value Tm will be 0.5 to 4.5 V. Since a value between 0 and 0.5 V or 4.5 to 5 V is output, it is considered abnormal. In this case, the voltage of the control power supply is 0 to 5 V, and the value of the torque value Tm is one setting example of the torque sensor (107, 107A). Similarly, the torque abnormality detection means 10-1B detects whether the torque value Ts output from the auxiliary torque sensor 107A is normal or abnormal. The detection principle is that if the auxiliary torque sensor 107 A is normal, its output value will be a value between 0.5 and 4.5 V, so it will be between 0 and 0.5 V or 4.5 and 5 V output is abnormal.

In addition, the torque abnormality detecting means 100 _ 1 C is such that the torque value Tm, which is the output of the main torque sensor 107, and the torque value Ts, which is the output value of the 畐 IJ torque sensor 107 A, are originally the same. If the difference AT r = IT m−T si between the two torque values is equal to or greater than a predetermined value, it is determined that the torque is abnormal. Another method of detecting an abnormality using the torque value T m and the torque value T s is, if the torque value T m and the torque value T s are normal, T m + T s = —constant value, or T m — There are anomaly detection methods that make use of characteristics such as T s = constant value, and these methods may be used.

The time for judging the abnormality is one cycle of the calculation by the CPU, and the judgment is made, for example, in about l ms. The torque abnormality detection means 10-1A, 10-0-IB, and 10-1C output, for example, "1" when abnormal, and "0" when normal.

The selection switches 10-4 are controlled by the OR section 10-5 and the AND section 10-7, and when the OR section 10-5 outputs S "1". In other words, when at least one of the torque abnormality detecting means 10 0-1 A, 10-1 B, and 10-1 C determines an abnormality, the selection switch 10-4 selects an alternative torque value, The substitute torque value is sent to the current command value calculator 120. On the other hand, when the AND section 10-7 outputs "1", the selection switch 10-4 selects the torque value Tm, which is the detection value of the torque sensor 107. That is, when all the outputs of the torque abnormality detection means 10-1A, 10-1B, and 10-1C output normal "0", the NOT section 10-0-6A, 10- 6 B, 10-6 Inverted by 6 C, all inputs of AND section 10 — 7 become “1”, and outputs of AND section 10 — 7 become “1”, select switch 10 — 4 Selects the torque value Tm. Therefore, the torque value Tm is input to the current command value calculator 120.

Such a control method is adopted when the torque value, which is the output of the torque sensor, is determined to be abnormal by at least one torque abnormality detecting means, and the electric power steering device is controlled with the alternative torque value, If the condition for returning control from the alternative torque value to the torque value output from the torque sensor is determined to be normal for all torque abnormality detection means, the safety of control of the electric power steering device can be ensured. It is.

Here, if the abnormality of the torque value continues beyond the predetermined time, it is considered that a serious failure such as a torque sensor has occurred.

Hereinafter, the determination of the determination that the torque sensors 107 and 107A are at fault will be described with reference to FIG.

In FIG. 15, the failure of the torque sensors 107 and 107 A is realized by the torque failure determination means 10-3. The torque failure determination means 10 0-3 outputs the outputs from the plurality of torque abnormality detection means 10 0-1 A, 10-1 B and 10-1 C to the delay sections (hereinafter referred to as TD) 1 0- Input to 3 A, 10-3 B, 10-3 C and OR the outputs from TD 10-3 A, TD 10-3 B, TD 10-3 C OR 10-3 D , And the output of the OR unit 10-3D is the failure determination result. TD is realized by a power counter or the like when a CPU is used as a control device. If the torque failure determination means 10-3A continues for more than a predetermined time t4, for example, 30 ms, when the abnormality "1" output from the torque abnormality detection means 10-1A continues, the torque sensor Determine the failure. Similarly, in the torque failure determination means 10-3B, the abnormality "1", which is the output of the torque abnormality detection means 10-1B, has continued for more than a predetermined time t5, for example, 3 Oms. In this case, it is determined that the torque sensor is out of order. Further, the torque failure determination means 10-3C outputs the torque when the abnormality "1" output from the torque abnormality detection means 10-1C continues for a predetermined time t6, for example, 40 ms. The determination that the sensor has failed is determined. The OR section 10-3D outputs "1" if at least one of TD IO-3A, 10-3B, and 10-3C outputs "1", and the torque sensor outputs Determine the failure. In other words, if the period during which even one of the torque abnormality detecting means 10-1A, 10-1B and 10-1C is considered to be abnormal independently exceeds a predetermined time, the torque sensor Determine the failure. Since the predetermined time of TD differs depending on the principle of detecting the abnormality of the torque sensor, the predetermined times t4, t5 and t6 of TD10-3A, 10-3B and 10-3C are different from each other. May be.

In the above description, the condition for determining that the torque sensor is faulty is a condition in which the time during which the torque abnormality detection means determines that the torque sensor is abnormal has continued for a certain period of time. There is a phenomenon that must be determined. This phenomenon will be described with reference to FIG.

Torque abnormality detecting means 1 0-1 A determines abnormality of the torque value Tm of the main torque sensor 107, and the principle of detection is that when the output is 0.5 to 4.5 V, it is normal. Up to 0.5 V or 4.5 to 5 V is judged as abnormal. In addition, the torque abnormality detecting means 10-1C is configured to calculate the deviation ΔT r = | between the output value Tm of the main torque sensor 107 and the output value T s of the auxiliary torque sensor 107A If Tm−T s I is equal to or greater than a predetermined value, it is determined that an abnormality has occurred.

It is assumed that the output cable of the main torque sensor 107 has a disconnection failure or a connector failure based on such a detection principle. When the output cable is disconnected, observe a short time of about 100 ms before and after the disconnection, and observe that the output value Tm of the torque sensor 107 input to the torque input processor 10 is between 0 V and 5 V. The hunting phenomenon occurs in a very short time. An example is shown in FIG. Torque abnormality detection means 1 0—1 A is abnormal at 0 to 0.5 V, normal at 0.5 to 4.5 V due to chattering where the torque value Tm fluctuates between 0 and 5 V, 4. An output as shown in Fig. 16 (A) is taken at 5 to 5 V according to the abnormality criterion.

On the other hand, the torque abnormality detecting means 1 0-1 C is such that, for example, when the auxiliary torque sensor 107 A is at the neutral point as the torque value of 2.5 V, the torque value Tm of the main torque sensor 107 is 2. Normal when the voltage rises and falls near 5 V, and an error is output when the voltage approaches 0 V or 5 V. Therefore, the output of the torque abnormality detecting means 10-1C is as shown in Fig. 16 (B), and the "1" and "0" signals which are different from the "1" and "0" signals in Fig. 16 (A) are alternated. It becomes “0” signal. If the allowable value for the deviation Δ Τ ι: is large, as shown in FIG. 16, the torque abnormality detecting means 10 0-1 may be used before the torque abnormality detecting means 10-1 A is switched from abnormal to normal. C changes from normal to abnormal, and all torque abnormality detecting means 10-1A, 10-1B, 10-1C will not be normal for a long time, for example, about 5 Oms. The alternative torque value control is continued for 50 ms for a long time.

Replacing this phenomenon with steering wheel operation, control is continued based on the alternative torque value when turning the steering wheel to the left at high speed driving, and when it is necessary to turn the handle to the right, the assist turns to the left It means that it will continue as it is. This is an undesirable phenomenon. Therefore, the torque sensor should be determined to be faulty and switched to the next best control method such as manual operation. is there.

The torque failure determining means for coping with such a phenomenon will be described with reference to FIG. 15, the torque input processing unit 10 is provided with torque failure determination means 10-3Y and torque failure determination means 10-3Z.

First, the torque failure determination means 10-3Y composed of the comparison section 103E and TD10-3F will be described. The torque failure determination means 1 0 3 Y compares the input value to the current command value calculation section 1 20 with the alternative torque value output from the alternative torque value calculation means 1 0-2 by the comparison section 1 0-3 E. Compare and determine whether the substitute torque value has been updated. Then, the comparison result of the comparison unit 10-3E is input to TD10-3F, and the alternative torque value exceeds the predetermined time t7 set by TD10-3F, for example, 50 ms. If has not been updated, the determination that the torque sensor has failed is determined.

Next, the torque failure determination means 10-3Z composed of TD10-3G will be described. The output of the OR section 10-5, which is the command for selecting the alternative torque value, is input to TD10-3G, and the period during which the alternative torque value is continuously selected is the predetermined time set by TD10-3G. If it continues for more than t8, for example, 60 ms, it is determined that the torque sensor is faulty. That is, the torque failure determination means 10-3Z determines that the torque sensor has failed if the alternative torque value control has continued for a long time. The difference between the torque failure determination means 1 0-3 G and the torque failure determination means 10 0-3 is as follows. The torque failure determination means 10-3 is the one where any one of the torque abnormality detection means 10-1A, 10-1B and 10-1C is abnormal for more than a predetermined time. Then, it is determined that the torque sensor is out of order. On the other hand, the torque fault determination means 10 0-3 Z has the torque abnormality detection means 10-1 A, 10 0-IB, 10 0-1 C like the chattering state abnormality. In addition, the period during which the abnormality is abnormal by itself is short, but when combined, the abnormality can be detected for a long time, even if the torque sensor fails.

The OR section 10-3H is for collecting the failure detection results of all the torque sensors. In this embodiment, the torque failure determining means 10-3 and the torque failure determining means 10-3 are used. The failure judgment result of F and 10-3Z is input. ₍ Thus, the special failure phenomenon that occurs when the wiring from the torque sensor is broken, etc. is also detected reliably, and the torque value from the torque sensor is When the torque sensor fails, the electric power steering device can be controlled by safe control such as manual control without the alternative torque value control that takes place for a long time continuing.

Although the case where the alternative torque value control is performed has been described above, an example in which the alternative torque value control is not performed will be described with reference to FIG.

The failure of the torque sensor occurs without executing the alternative torque value control. It is necessary to detect the failure of the torque sensor reliably. However, in the past, the torque failure determination means using the torque failure determination means 10_3, fi TD TD 10-3A, 10-3B and 10-3C in Fig. In the case where the abnormality has continued for a long time, for example, when the abnormality has continued for the time T1 or more, it has been determined that the torque sensor has failed. However, a plurality of torque abnormality detecting means 10-1A, 10-1B, 10-1C as described with reference to FIG. 16 are used as independent torque abnormality detecting means such as chattering. In this case, the abnormal period is short, but when the torque abnormality detecting means 10-1A, 10-1B and 10-1C are combined, the abnormal period continues for a long time. Conventionally, it could not be detected as a failure of the torque sensor.

However, as shown in Fig. 18, the torque abnormality detection means 10-1A, 1 By combining 0—IB, 10—1C, OR section 10—5 and TD 10—3G, the period during which multiple torque abnormality detection means are abnormal by themselves, such as chattering, is short. It is time, but when the torque abnormality detection means 10-1 A, 10-1 B, and 10-1 C are combined, it is possible to ensure that the abnormal period continues for a long time, for example, the predetermined time t 8 or more. And the torque sensor can be determined to be defective.

Therefore, regardless of the alternative torque value control, the period during which a plurality of torque abnormality detection units are abnormal alone such as chattering is short, but the period during which a plurality of torque abnormality detection units are abnormal is long. An abnormality that continues for a certain period of time, in other words, an abnormality in which at least one of the plurality of torque abnormality detection means is determined to be abnormal for more than a predetermined time is reliably detected. Can be determined. Furthermore, by executing the control corresponding to the failure of that, then _c may provide a control apparatus for a good feeling handle which can operate the electric power steering apparatus, in the abnormal term of the torque sensor is used to control A third embodiment capable of accurately estimating the substitute torque value will be described.

FIG. 19 is a control block diagram showing a third embodiment of the present invention. The sensor signal Tr detected by the torque sensor 107 is input to the main torque detecting unit 107B as the main torque detecting unit and to the auxiliary torque detecting unit 107C as the auxiliary torque detecting unit. . The main torque detector 107B and the auxiliary torque detector 107C are for detecting the torque value of the steering wheel 101 from the sensor signal Tr output from the torque sensor 107, It is composed of an electronic circuit such as an arithmetic and logic unit and software processing. The main torque detection unit 107B outputs a main torque detection value Tm, and the sub torque detection unit 107 outputs a sub torque detection value Ts. Main torque detector 1 0 7 B and auxiliary torque The torque detection unit 107 C constitutes a dual system for torque detection. In this embodiment, one torque sensor 107 is used in common.However, two torque sensors for the main torque detection value and the auxiliary torque detection are prepared, and the torque sensor stage is doubled. The system may be configured.

The main torque detection value T m output from the main torque detection unit 107 B and the sub torque detection value T s output from the sub torque detection unit 10 C are input to the torque input processing unit 10 respectively. Is done. Since the details of the torque input processing unit 10 will be described later in detail, the part related to motor control at the subsequent stage of the torque input processing unit 10 will be described first. The torque value T output from the torque input processor 10 is input to the current command value calculator 120, and the current command value calculator 120 calculates the current command value Iref. The current command value Iref is input to the subtraction unit 121 via the limiter 11 controlled by the torque input processing unit 10. In the subtraction unit 121, a deviation between the current command value Iref and the detected value Im of the motor current is calculated. The deviation is input to a current control unit 122 constituted by a proportional integral or the like, and the current control unit 122 sets a duty ratio of the inverter control PWM control which is an example of the motor drive unit 123. Output. The motor drive unit 123 supplies the motor current by the PWM control according to the duty ratio to the motor 108, and the motor 108 outputs a torque corresponding to the torque value specified by the steering handle. .

The above is the description of the basic part of the motor control of the present embodiment. Next, the torque input processing unit 10 which is a main part of the present embodiment will be described.

The main torque detection value Tm from the main torque detection unit 107B and the auxiliary torque detection value Ts from the auxiliary torque detection unit 107C are input to the torque input processing unit 10. The torque input processing unit 10 includes a torque abnormality detection unit 10-1 that receives the main torque detection value Tm and the auxiliary torque detection value Ts as input, and an alternative torque value calculation unit 10-2. Torque abnormality detection means 1 0-1 The sensor 107 has a function of detecting an abnormality of the main torque detector 107B or the 畐 ij torque detector 107C. The substitute torque value calculating means 10-2 uses the main torque detection value Tm and the auxiliary torque detection value Ts to generate the torque sensor 107, the main torque detection unit 107B or the auxiliary torque detection unit 107. When C is abnormal, an alternative torque value Ta of the torque used in place of the main torque detection value Tm is calculated.

The torque input processing unit 10 further includes torque failure determination means 10-3 and a selection switch 10-4. The selection switch 10-4 selects either the alternative torque value T a output from the alternative torque value calculation means 10-2 or the main torque detection value T m output from the main torque detector 107B. Is selected based on the output of the torque abnormality detection means 10-1. In addition, the torque failure determination means 10-3 uses the abnormality detection signal from the torque abnormality detection means 10-1 to provide a torque sensor 107 and a main torque when the abnormal state continues for more than a predetermined time. The detector 107B or the auxiliary torque detector 107C has a function to determine that it is faulty. If it is determined that it is faulty, the limiter 11 Control the trip value.

Next, an operation example of the torque input processing unit 10 will be described with reference to the flowchart of FIG.

For example, since the normal value of the main torque detection value Tm is 0.5 V or more and 4.5 V or less, outputting 0 V or 5 V means that the main torque detection value Tm is abnormal. Then, when the abnormal state continues for a predetermined time, for example, more than 3 Oms, the failure of the main torque detection value Tm is determined. The flowchart of FIG. 20 is an example showing the alternative torque value control, torque abnormality detection, and torque failure determination operation in the case of the above-described torque abnormality or torque failure determination. First, the main torque detection value Tm and the auxiliary torque detection value Ts are read from the main torque detection unit 107B and the auxiliary torque detection unit 107C, respectively (step S 1), judge whether the main torque detection value Tm is 0.5 V or less or 4.5 V or more. If the value is between 0.5 V and 4.5 V, it is normal (YE S) It is judged, and if it is 0.5 V or less or 4.5 V or more, it is judged as abnormal (NO) (step S2). If the main torque detection value Tm is normal, the detection counter is cleared (step S3). The detection counter measures the abnormality duration used to determine whether the torque sensor 107 or the main torque detector 107B that outputs the main torque detection value Tm is faulty. In this embodiment, if the abnormality of the main torque detection value Tm continues for more than 30 ms, the failure is determined.

After the detection counter is cleared, the past main torque value Tm and the past auxiliary torque detection value Ts are updated and stored (step S4). FIG. 21 shows a flowchart for updating the past torque values, which will be described later. After updating the past torque value, the main torque detection value Tm is used as the torque value T used for motor control (step S6). In other words, the selection switches 10-4 select and output the main torque detection value Tm.

On the other hand, if it is determined in step S2 that the main torque detection value Tm is abnormal, the detection counter is counted up once (step S6), and the detection counter counts the torque sensor 107 and the main torque detection unit 1 It is determined whether or not 07 A has exceeded the set value of the power point, which is a predetermined value of the time for determining the failure is determined (step S7).

Then, while the duration of the abnormality is equal to or less than the predetermined value (NO), the alternative torque value control is executed without determining that the torque sensor or the like is faulty. In the alternative torque value control, the control of the motor 108 is performed using the alternative torque value Ta instead of the abnormal main torque detection value Tm detected by the torque sensor 107, and the motor control is abnormal. Then, an alternative torque value Ta that does not result in a difference is calculated (step S8). An example of a method for calculating the substitute torque value Ta Will be described later with reference to the flowchart of FIG. When the alternative torque value Ta is set, the alternative torque value Ta is input to the torque value T as the output of the torque input processing unit 10 (step S9), and the alternative torque value Ta is output as the torque value T. Yes (step S5).

On the other hand, if the abnormal time continues for a predetermined value or more in step S7 (YES), that is, if the count of the value detection counter exceeds the set value (YES), it is determined that a failure has occurred, and the limiter 1 1 A slashing process for narrowing down the torque value using is performed (step S10).

Next, the update of the past main torque detection value Tm and sub torque detection value Ts in the upper air step S4 will be described with reference to the flowchart of FIG.

The example of FIG. 21 is an embodiment in which the substitute torque value Ta is calculated using five past torque values. First, a one-step new past main torque value Tm 2 and sub torque detection value T s2 are substituted for the main torque detection value T ml and the sub torque detection value T s 1 (step S 14). Similarly, the main torque detection value Tm 2 and the auxiliary torque detection value T s 2 are substituted by the one-step new past main torque value Tm 3 and the auxiliary torque detection value T s 3, respectively (step S 15). The previous main torque value Tm4 and the auxiliary torque detection value Ts4, which are new by one step, are substituted for the detection value Tm3 and the auxiliary torque detection value Ts3, respectively (step S16). Further, the main torque detection value Tm 4 and the auxiliary torque detection value T s 4 are respectively substituted by the past main torque value Tm 5 and the auxiliary torque detection value T s 5 which are new by one step (step S 17), and the main torque detection value The new main torque value Tm and auxiliary torque detection value Ts, which is one step new, are substituted for Tm5 and auxiliary torque detection value Ts5 (step S18).

The current main torque value Tm and auxiliary torque detection value Ts are also calculated in the following steps. When it is used to calculate the alternative torque value Ta when the torque detection value becomes abnormal in the step, it is the past torque detection value one step before. In addition, if the performance of the CPU and memory is good, high-speed processing is possible, and the memory capacity is sufficient, the past torque value is calculated using the five or more past torque values to calculate the substitute torque value Ta. Is also good. Conversely, the alternative torque value Ta may be calculated using five or less past torque values. The number of past torque values for calculation may be determined based on the relationship between the accuracy of the substitute torque value Ta and the performance of the CPU and the capacity of the memory.

Next, the contents of the alternative torque value setting step (step S8) for calculating the alternative torque value Ta will be described with reference to the flowchart of FIG.

First, in FIG. 22 (A), the difference ΔT i = I Tmi−T si | in the combination of the main torque detection value Tmi and the auxiliary torque detection value T si of the past torque is calculated. For example, ΔΤ1 = IT ml-Ts1I, ΔT2 = | Τm2-Ts2 |. (Step S21). Next, the combination (Tmk, Tsk) that minimizes the difference ΔT i is selected (step S22). If there are a plurality of combinations (Tmk, Tsk) with the smallest difference ΔT i, select the latest combination (step S23). Then, using the combination (Tmk, T sk) that minimizes the difference ΔT i and the latest combination (Tmk, T sk), if the difference AT i is less than or equal to the predetermined value Δ Τ 1 imit For example, the main torque detection value T mk or the auxiliary torque detection value T sk is selected as the alternative torque value T a (step S24). The main torque detection value Tmk or the auxiliary torque detection value Tsk of the combination (Tmk, Tsk) is selected as the alternative torque value Ta because the difference value Ti is a predetermined value ΔT1 that is sufficiently small. If imit or less, the primary torque detection value T mk and the secondary torque detection value T sk detected almost the same torque detection value This means that both torque detection values are correct, and there is no problem in using either torque detection value as the substitute torque value T a.

An example of another method of selecting the alternative torque value Ta will be described with reference to the flowchart of FIG. 22 (B). In FIG. 22 (B), first, the difference ΔT i = | Tmi_T si | in the combination of the main torque detection value Tmi and the auxiliary torque detection value T si of the past torque is calculated (step S 21). . For example, Δ Τ 1 = I Tml — T s l | and Δ T 2 = | Tm2 — T s 2 |. Next, the combination (Tmk, Tsk) that minimizes the difference ΔTi is selected (step S22). If there are a plurality of combinations (Tm k, T s k) with the smallest difference ΔT i, the latest one is selected (step S 23). Then, whether to select the primary torque detection value Tmk in the (Tmk, T sk) of the latest combination and the alternative torque value T a or the auxiliary torque detection value T sk in which the difference ΔT i is the smallest is determined. Then, a torque detection value closer to the torque value Tn indicating the intermediate value of the steering wheel is selected (step S25). In the case of FIG. 22 (B), the predetermined value may not be as small as that of FIG. 22 (A), but it is better to add a condition that the difference Δ 量 i is equal to or smaller than the predetermined value. It is safe.

The reason for calculating such an alternative torque value Ta is that if the torque detection value is normal, the main torque detection value Tm and the auxiliary torque detection value Ts should be essentially the same, so the difference is small. It is preferred that the alternative torque value T a be the same. Also, if the difference is the same, it is clear that it is preferable to select the latest torque detection value closer to the present as the alternative torque value used for the current control. Whether the main torque detection value Tm or the sub torque detection value Ts is selected from among the selected torque detection values is determined by the case where an abnormal torque detection value is indicated by 0 V indicating a ground fault. And 5 V, which indicates a short-to-power fault, and hunting. The interval is alternately repeated at high speed. Considering the fact of such a failure phenomenon, the torque value Tn indicating the intermediate value of the steering wheel is closer to 2.5 V, which is the intermediate value between 0 V and 5 V, and the alternative torque value T a Is preferable. The reason for selecting the value closer to the intermediate value is that the value closer to the intermediate value is often smaller and safer.

The method of calculating the alternative torque value Ta using both the detected torque values of the combination (T mk, T sk) is not limited to the method of FIG. 22 (A) or (B) described above. Absent.

As described above, by executing the alternative torque value control using the past main torque detection value and the past auxiliary torque detection value, it is calculated from the past torque detection value as compared with the case where there is one torque detection value. The accuracy of the alternative torque value is further improved. In the case of an abnormality that causes chattering, it is rare that both the main torque detection value Tm and the auxiliary torque detection value Ts cause chattering, and if either is the correct torque detection value Therefore, using two torque detection values, the main torque detection value Tm and the auxiliary torque detection value Ts, is effective in calculating a correct alternative torque value. FIG. 23 shows the relationship between the output (torque value) of the torque sensor and the motor current when the output value of the torque sensor suddenly becomes zero using the torque input processing unit 10 of this embodiment. I have. Even if the torque value suddenly becomes zero, the substitute torque value is immediately used instead of the abnormal torque value, so that the motor current maintains the value immediately before the torque value became abnormal. Then, the motor current maintains the previous value until the torque sensor is determined to be faulty, and the motor current gradually decreases after the torque sensor is determined to be faulty. Compared with Figs. 4 and 5, which show the results of the conventional control method, the motor current does not reverse the polarity immediately before the torque value becomes abnormal, and does not give a sense of incompatibility to the steering operation. FIG. 24 shows the relationship between the output of the torque sensor (worst case) and the motor current when the torque sensor output value causes chattering and breaks down, using the torque input processing unit 10 of this embodiment. Shows the relationship. If the torque value is determined to be abnormal due to chattering, a substitute torque value is calculated using the past normal torque value, and the motor current is controlled based on the substitute torque value. Therefore, the motor current outputs a current that does not greatly differ from the motor current immediately before chattering occurs. Furthermore, after the failure is detected, the motor current is gradually attenuated. This result is compared with Fig. 6 showing the result of the conventional control method. In the case of the conventional control method, a motor current of the opposite polarity to that before the torque sensor becomes abnormal is generated, and the motor fluctuates thereafter, which is undesirable for the driver. It is good to gradually attenuate the motor current after detecting a failure, but it is not preferable because the motor current immediately before the attenuation also attenuates from the current of the opposite polarity. Even in the worst case, the control method according to the present embodiment is clearly preferable to steering control compared to the conventional control method.

As described above, according to the present invention, until the torque sensor or the torque detection unit is determined to be faulty, the motor control is performed using the accurately calculated alternative torque value instead of the abnormal torque detection value. Therefore, even if the torque sensor or torque detector becomes abnormal, even if the predetermined time until the torque sensor or torque detector is determined to be faulty is long enough to prevent erroneous detection, operation of the steering wheel without any uncomfortable feeling Can be realized.

In the above-described embodiment, as an example of determining that the torque sensor or the torque detector is abnormal or faulty, the main torque detection value Tm is in a normal range (0.5 V or more and 4.5 V or more). Although it is assumed that the torque sensor and the torque detector are abnormal or faulty, there are other methods for detecting abnormalities and determining failures. Such an embodiment is described with reference to FIG. Will be explained.

The difference from the above-described embodiment is that the torque abnormality detecting means 10-1 has a plurality of torque failure abnormality detecting means 10-1A, 10-IB, 10-1C having different principles. Therefore, the switching judgment of the selection switches 10-4 is as follows. Abnormality of any one of torque abnormality detection means 10-1A, 10-1B, 10-1C (If the abnormality is abnormal, set the output of each torque abnormality detection means to "1".) The output of the torque abnormality detection means 10-1A, 10-1B, 10-1C is input. Based on the output of the R section 10-5, the alternative torque value calculation means 10- Select the alternative torque value Ta that is the output of 2. Conversely, if all of the torque abnormality detection means 1 0-1 A, 10-1 B, and 10-1 C are not abnormal, that is, they are all normal (the output of each torque abnormality detection means is "0" when normal) In the case of, the torque abnormality detection means 10-1 A, 10-1 B, and 10-1 C-NOT part which receives each output as input-10-6 A, 10-6 B, 1 ◦ — Based on the output of the ND section 10 — 7 that receives the output of 6 C, the selection switch 10 — 4 outputs the main torque detection value Tm that is the output of the main torque detection section 107 A. Select

Here, an example of the detection principle of the torque abnormality detecting means 10-1A, 10-1B, 10-1C will be described. The torque abnormality detection means 10-1A is the same as the torque abnormality detection means used in the embodiment of FIG. 19, and determines that the main torque detection value Tm is out of the normal range as abnormal. It is. Torque abnormality detection means 10-1B is a torque abnormality detection means that determines that an abnormality occurs when the auxiliary torque detection value Ts is not in the normal range (0.5 V or more and 4.5 V or less). In addition, since the torque abnormality detecting means 10-1C is supposed to have the same primary torque detection value T s and secondary torque detection value T s, the primary torque detection value T s and the secondary torque detection value T s This is a torque abnormality detection means that determines that the difference is out of the normal range as abnormal. Also, the difference between the torque failure determination means 10_3 and the embodiment of FIG. 19 is that the torque abnormality detection means 10-1 has a plurality of torque abnormality detection means 10-1A, 10-1B, Along with having 10-1 C, multiple delay sections (hereinafter referred to as TD sections) 10-3 A, 10-3 B, 10-3 C It is. That is, if the output of the torque abnormality detecting means 10-1A continues to be abnormal for more than the predetermined time t4, for example, 30 ms, the TD section 10-3A will output the torque sensor 107 It is determined that the torque detector 107A is faulty. Similarly, when the output of the torque abnormality detecting means 10-1B is abnormal for more than a predetermined time t5, for example, 30 ms, the TD section 10-3B outputs the torque sensor 107 The auxiliary torque detector 107B is determined to be faulty. Further, the TD section 10-3C outputs the torque sensor 107 and the main sensor when the output of the torque abnormality detecting means 10-1C is abnormal for more than a predetermined time t6, for example, 30 ms. It is determined that the torque detecting unit 107A or the auxiliary torque detecting unit 107B is faulty.

Then, based on the output of the OR unit 10-3D, which receives the output of the torque failure determination means 10_3A, 10-3B, and 10-3C (referred to as "1" due to failure) as input. However, when it is determined that the torque sensor or the torque detecting unit is faulty, the limiter 11 is controlled, and a temporary reduction process for narrowing down the current command value I ref is executed.

This embodiment has a plurality of torque abnormality detecting means 10 -1 A, 10 -1 B _s 10 1: LC. Therefore, the switching reason of the selection switch 10-4 is as follows. Abnormality detecting means 10 0-1 A, 10-1 B, 10-1 C If any of the abnormalities is detected, the selected switch 10-4 replaces the main torque detection value Tm. To select an alternative torque value Ta. Conversely, if a plurality of torque abnormality detection means 10_1A, 10_1B, 10_1C are all normal, the selected switch 10-4 will determine the main torque detection value. Tm select.

On the other hand, the alternative torque value calculation means 10-2 of the present embodiment is calculated based on an alternative torque value calculation step shown in the flowchart of FIG.

In the case of a dual system in which the main torque detection value Tm and the auxiliary torque detection value Ts are detected. It is unlikely that there are multiple abnormality detection means and failure determination means corresponding to the dual system as in the second embodiment. Of course. As described above, even if there are a plurality of abnormality detection means and failure determination means, if the torque sensor or the torque detection unit is abnormal, the previous main torque detection value Tm and the auxiliary torque detection value Ts are used. The substitute torque value does not give a sense of incongruity to the handle operation until the torque sensor and the torque detection unit become abnormal and are determined to be faulty.

As described above, according to the present invention, the alternative torque value using the past main torque detection value Tm and the auxiliary torque detection value Ts is one of the alternative torque values even if an abnormality occurs in the torque detection. It is highly likely that correct torque detection is being performed, and the alternative torque value is calculated using the correct past torque detection value. As a result, compared to the alternative torque value that can only use the main torque detection value Tm, a comfortable steering operation is realized until the torque sensor and torque detection unit become abnormal and the failure is confirmed. it can. Especially in the case of a chattering error that occurs when the wiring for torque detection is broken. Both the main torque detection value Tm and the auxiliary torque detection value Ts are unlikely to generate chattering, so Valid. Industrial applicability

The electric power steering control device according to the present invention provides an electric power steering system capable of ensuring a safe steering operation without giving an uncomfortable feeling to the steering operation even when a torque sensor for detecting a steering torque of the steering wheel becomes abnormal. Suitable for use in equipment.

Claims

The scope of the claims

1. A motor that applies a steering assist force to the steering system of the vehicle and at least one or more torque sensors that detect the steering force acting on the steering wheel, and controls the motor based on the output value of the torque sensor At least one or more torque abnormality detecting means for detecting an abnormality in the output value of the torque sensor, and a past normal value before the output value of the torque sensor becomes abnormal. A torque input processor configured to calculate an alternative torque value based on an output value of the torque sensor, wherein when the output value of the torque sensor is abnormal, instead of the output value of the torque sensor, A control device for an electric power steering device, wherein the motor is controlled based on the substitute torque value.

2. A torque failure determination means is provided for determining that the torque sensor is faulty when the output value of the torque sensor continues for a certain period of time. If the output value of the torque sensor is abnormal, the torque is determined. The electric power steering device according to claim 1, wherein the motor is controlled based on the alternative torque value instead of the output value of the torque sensor even before the determination that the sensor is faulty is finalized. Control device.

3. The claim according to claim 1 or 2, wherein the alternative torque value is an average value of n (natural number) samples of the output value of the torque sensor immediately before the output value of the torque sensor becomes abnormal. Control of electric power steering device

4. The substitute torque value is immediately before the output value of the torque sensor becomes abnormal. 3. The control device for an electric power steering apparatus according to claim 1, wherein the control value is a weighted average value of n (natural number) samples of the output value of the torque sensor.

5. The method according to claim 1, wherein the alternative torque value is a value calculated by the least square method from n (natural number) samples of the output value of the torque sensor immediately before the output value of the torque sensor becomes abnormal. 3. The control device for the electric power steering device according to item 2.

6. The substitute torque value is a value obtained by creating the following equation (n_l) from an n (natural number) sample of the output value of the torque sensor immediately before the output value of the torque sensor becomes abnormal, and predicting the current value. 3. The control device for an electric power steering device according to claim 1, wherein the control device is:

7. A plurality of torque abnormality detection means for detecting abnormality of the torque sensor based on the output value of the torque sensor, and based on past normal output values of the torque sensor before the output value of the torque sensor becomes abnormal. And a substitute torque value calculating means for calculating a substitute torque value.When it is determined that at least one of the plurality of torque abnormality detection means is abnormal, based on the substitute torque value instead of the output value of the torque sensor. Controlling the motor and controlling the motor based on the alternative torque value; determining that all of the plurality of torque abnormality detection means are normal; replacing the alternative torque value with the torque sensor; The control device for an electric power steering device according to claim 1, wherein the control is performed using an output value.

8. It is determined that one of the plurality of torque abnormality detection means continues to be abnormal. The control device for an electric power steering device according to claim 7, further comprising: a torque failure determination unit that determines a determination that the torque sensor is faulty when the time period to be determined exceeds a predetermined time.

9. The torque failure determination device according to claim 7, further comprising: a torque failure determination unit that determines that the torque sensor is faulty when the alternative torque value is not updated even after a predetermined time. Control unit for electric power steering system.

10. An electric power steering device comprising: a motor for applying a steering assist force to a steering system of a vehicle; and a torque sensor for detecting a steering force acting on a steering wheel, and controlling the motor based on an output value of the torque sensor. The control device according to claim 1, further comprising: a plurality of torque abnormality detecting means for detecting an abnormality of the torque sensor based on an output value of the torque sensor; The control device for an electric power steering device is characterized in that, when the time period for determining that the torque sensor exceeds a predetermined time period, the determination that the torque sensor is out of order is determined.

1 1. An electric power steering device that includes a motor that applies a steering assist force to a steering system of a vehicle, and a torque sensor that detects a steering force acting on a steering wheel, and controls the motor based on an output value of the torque sensor. The control device according to claim 1, further comprising a plurality of torque abnormality detecting means for detecting an abnormality of the torque sensor based on an output value of the torque sensor, wherein at least one of the plurality of torque abnormality detecting means is abnormal. A control device for an electric power steering device, characterized in that when the determination period continues and exceeds a predetermined time, it is determined that the torque sensor is out of order.

12. A main torque detecting means for detecting a main torque detection value Tm based on an output of the torque sensor, a sub-torque detecting means for detecting a sub-torque detection value Ts based on an output of the torque sensor, A torque abnormality detecting means for detecting abnormality of the main torque detection value Tm or the auxiliary torque detection value Ts, and a past normal before the main torque detection value Tm or the auxiliary torque detection value Ts becomes abnormal The alternative torque value Ta is calculated based on the past normal auxiliary torque detection value Ts before the main torque detection value Tm and the main torque detection value Tm or the auxiliary torque detection value Ts become abnormal. When the main torque detection value Tm or the auxiliary torque detection value Ts is detected to be abnormal, the alternative torque value T is used instead of the main torque detection value Tm. The motor according to claim 1, wherein the motor is controlled based on a. Control device for electric power steering equipment.

13. A torque failure determination means for determining that a failure has occurred when the main torque detection value Tm or the auxiliary torque detection value Ts is abnormal for a predetermined period of time; If the detection means detects that the main torque detection value Tm or the auxiliary torque detection value Ts is abnormal, the main torque can be maintained even before the torque failure determination means determines that a failure has occurred. 13. The control of the electric power steering apparatus according to claim 12, wherein the motor is controlled based on the alternative torque value Ta instead of the torque detection value Tm.

14. The alternative torque value T a is the main torque detection value T m and the auxiliary torque detection value T at the same time in the past before the main torque detection value T m or the sub torque detection value T s becomes abnormal. s and the past simultaneous The control device for an electric power steering device according to claim 12 or 13, wherein the request is calculated using the main torque detection value Tm and the auxiliary torque detection value Ts of the point.

1 5. If there are a plurality of combinations (Tm, Ts) of the main torque detection value Tm and the auxiliary torque detection value Ts at the same time in the past where the difference amount is minimum, the latest combination (Tm, Ts) 15. The control device for an electric power steering device according to claim 14, wherein:

1 6. The alternative torque value T a is a torque neutral value indicating that the steering wheel indicates a neutral point, out of the main torque detection value Tm and the auxiliary torque detection value T s at the same time in the past at which the difference amount is minimum. 16. The control device for an electric power steering device according to claim 14, wherein the detected torque value is a torque detected value that is a closer torque value.

1 7. The torque abnormality detecting means detects abnormality of the torque sensor based on the main torque detection value Tm, the auxiliary torque detection value Ts, or the main torque detection Tm and the auxiliary torque detection value Ts. A control device for an electric power steering device according to any one of claims 14 to 16.